1. Field of the Invention
The invention relates to exercise and sports, particularly to applications in which recovery of a person from a fitness exercise performed by him/her is controlled.
2. Brief Description of the Related Art
Recovery after exercising is important both to metabolism and muscle care. Stress pain resulting from exercising can be reduced considerably by a well-performed recovery exercise. In that case recovery is achieved in shorter time and the capability of the muscles and the system to perform the next exercise improves considerably. The most important function of the recovery exercise is to remove any lactic acid, i.e. lactate, accumulated in the body quickly and efficiently so that the lactate does not cause pain and post-exercise stress in the muscles. For this reason, the recovery exercise has to be performed at a stress level which prevents build-up of additional lactate, but enables effective removal of lactate from the body. Thus the recovery exercise is performed below the anaerobic threshold.
Nowadays various instructions and rules are used in sports coaching and training to keep recovery exercise at a certain adequate level for a predetermined time. For example, the exercising person may be told to recover from exercising by walking for 10 minutes or by keeping the heart rate at 120 beats/minute for 10 minutes.
The prior art method of recovering from a fitness exercise has considerable disadvantages. It is clear that the above-mentioned instructions are very general and by no means optimal for achieving as efficient recovery as possible. The above-mentioned instructions take the characteristics of an exerciser into account only indirectly, e.g. a coach may give different instructions for performing recovery exercise to athletes with different fitness levels.
The object of the invention is to provide an improved method of controlling a fitness exercise. This is achieved with the method to be described in the following. The method concerns controlling recovery of a person from a fitness exercised performed by him/her. The method comprises controlling a recovery exercise following the fitness exercise so that it is performed at a heart rate level below the threshold value of heart rate, heart rate variation being higher than a preset threshold value of heart rate variation at heart rate levels lower than the-threshold value of heart rate.
The invention also relates to a heart rate measuring arrangement. The heart rate measuring arrangement comprises measuring means for obtaining heart rate information, forming means for forming control information from the heart rate information obtained by measuring to control the recovery exercise, display means for presenting the formed control information.
The preferred embodiments of the invention are disclosed in the dependent claims.
The invention relates to a method and apparatus for controlling recovery of a person from a fitness exercise performed by him/her. In this description the fitness exercise refers to a physical exercise which is at least partly performed at a workload level exceeding the anaerobic level, in which case lactate is accumulated in the muscles of the person""s body. The recovery exercise means the exercise phase that follows the actual fitness exercise or competitive exercise which is mainly performed at a workload level below the anaerobic level. Controlling means control information provided e.g. by a heart rate monitor, such as the heart rate level, the heart rate limits within which the recovery exercise should be performed, and the time preferably used for the recovery exercise.
In a preferred embodiment of the invention, an anaerobic threshold value, i.e. the threshold value of heart rate, is found on the basis of changes in heart rate variation. Here heart rate variation means temporal variations in heart beats around the expected moments at which the heart should beat. In a preferred embodiment, the variation is calculated as moving standard deviation, but it, can also be calculated by another prior art mathematical method, e.g. by a method which utilizes the distribution function between the heart rate and the heart rate variation. As a function of heart rate, the heart rate variation naturally decreases as the heart rate, i.e. the heart beat frequency, increases. FIG. 1 illustrates variation as a function 100 of heart rate, i.e. the x axis 104 shows the heart rate as per cent of the maximum heart rate and the y axis 102 shows standard deviation as milliseconds around the expected moment at which the heart should beat. FIG. 1 illustrates dependency between the heart rate variation and the heart rate, which applies to the majority of people. When the heart rate level is e.g. 40% of the maximum heart rate, the heart rate variation is between 15 to 25 milliseconds. The maximum heart rate means the heart rate value that can be calculated e.g. by the formula (220xe2x88x92age), in which case the maximum heart rate of a 40-year old person is 180. The maximum heart rate can also be measured at the maximal workload or determined from the person""s physiological properties using a neural network, for instance. It can be seen from FIG. 1 that as the heart rate level approaches the maximum heart rate, the heart rate variation decreases considerably. The angular point of heart rate variation, i.e. the change point 106, is achieved at a heart rate level which is usually about 62 to 65% of the maximum heart rate, but may also vary in a wider range, e.g. 55 to 70% of the maximum heart rate. The change point 106 of heart rate variation is connected to the anaerobic limit point 106b of energy metabolism. It can be seen from FIG. 1 that the anaerobic limit point 106b is at a slightly higher heart rate level, i.e. 15 to 25 beats higher, than the change point 106 of heart rate variation. At heart rate levels above the anaerobic limit point 106b exercise is anaerobic, whereas at heart rate levels below the limit point exercise is aerobic. The intersection point of the change point 106 is about 4 milliseconds at the y axis, but may vary e.g. from 3 to 5 milliseconds.
In this description the fitness exercise refers to a physical exercise which is at least partly performed at a workload level exceeding the anaerobic limit, in which case lactate accumulates in the muscles of the person""s body. Lactate concentration can be estimated for a given period, e.g. a few hours before and after the fitness exercise, and thus the invention is not limited to the actual performance of the fitness exercise. A fitness exercise can be divided e.g. into the following phases: warm-up, active phase, recovery phase, in which case the fitness exercise is preceded and followed by a rest. Different phases can be defined and distinguished from one another e.g. on the basis of heart rate levels and/or workload levels. Then the recovery phase, for example, can be defined as an exercise level where the heart rate level drops from 130 beats/minute to a rest level of 70 beats/minute. The recovery phase is considered to begin when the heart rate level is below the limit of the active phase, i.e. 130 beats/minute, for two minutes, for instance.
In a preferred embodiment of the invention the exercising person monitors his/her heart rate at least at the end of the fitness exercise. At the beginning of the recovery exercise, the exerciser starts to walk, for example, so that the heart rate drops to a heart rate value below the change point of heart rate variation. For the recovery to be maximally efficient, it should be performed as close to the change point as possible, i.e. at a heart rate which is about 55 to 60% of the maximum heart rate.
In another preferred embodiment of the invention, the physical condition of the exercising person is also taken into account in the calculation of the change point of heart rate variation. Physical condition can be defined e.g. as the maximal oxygen uptake, which can be determined e.g. by measuring the maximal oxygen uptake at the maximal workload or by forming an estimate by means of a neural network, into which one or more physiological parameters are fed as input parameters and/or several stress parameters that describe the workload. The physical condition affects curve 100 shown in FIG. 1 so that the change point of heart rate variation of a fit person is at a higher heart rate level than that of an unfit person. However, the proportional share of heart rate variation of the maximum heart rate is the same for both these persons. Thus a fit person can exercise at a higher workload without the exercise being anaerobic. The distance between the points 106 and 106b depends on the person""s condition and lactate properties. In the case of a person with a very good condition, for example, the distance between the points is larger, which is taken into account in an embodiment by considering the person""s condition in calculation and determination of controlling. In determination of point 106b a prior art lactate tolerance test, for example, is used. In the test, blood tests are used to locate the threshold of the angular coefficient of the lactate curve under stress, which corresponds to the heart rate level at point 106b. 
In a preferred embodiment recovery from a fitness exercise is controlled by means of the vanishing point of heart rate variation and the lactate that has accumulated in the body during exercise. According to an embodiment, the amount of lactate in the body is estimated by a two-part mathematical model which is described in greater detail in FIG. 2. In this specification the mathematical model refers to a set of mathematical operations and rules for determining output parameter values from the input parameter values. Mathematical operations include arithmetic operations, such as addition, subtraction and multiplication. The mathematical model can naturally be implemented as a table or a database, in which case the output parameter value corresponding to a given input parameter is read directly from the database. It is clear that the model may consist of only one part or of more than two parts. One or more parameters 202 representing the person""s heart rate, such as the average heart rate, standard deviation of the heart rate or the like, are fed into the first part 200 of the model as input parameters. The input data of the model also comprise one or more stress parameters 204 describing the exercise workload, such as running speed or pedalling speed of the exercise bike. The third set of input parameters for the model consists of one or more physiological parameters 206 of the person, such as height, weight or gender. The above-mentioned input parameter sets 204 to 206 are optional, i.e. they may be included in the model separately, simultaneously, or be omitted from the model. In an embodiment of the invention the first part 200 of the model is implemented as a neural network which has been trained with user data comprising information on hundreds or even thousands of users. In an embodiment of the invention, the first part of the model provides the person""s stress level 208 during exercise as the output. The output parameter set 210 provided by the model represents one or more fitness parameters which describe the person""s physical condition, such as the maximal oxygen uptake or the fitness index.
The input parameters to be fed into the second part 212 of the model include the above-mentioned information representing the exercise stress level 208 and optionally one or two fitness parameters 210 describing the user""s condition. In a preferred embodiment of the invention, the second sub-model 212 is a mathematically formed physiological model which gives the amount 214 of lactate in the person""s body as the output parameter on the basis of the input parameters. The amount 214 of lactate is used as the input parameter of control routines 216 which control removal of lactate from the body, using the control output 218 for monitoring that the duration and efficiency of the recovery exercise are sufficient.
In the solution of the invention for controlling a recovery exercise, the person whose recovery is to be monitored, preferably uses a heart rate monitor. The heart rate monitor is a device employed in sports and medicine, which measures human heart rate information either from an electrical impulse transmitted by the heart or from the pressure produced by the heart beat on an artery. Generally, the heart rate monitors comprise an electrode belt to be fitted around the user""s chest to measure the heart rate by means of two or more electrodes. The electrode belt transmits the measured heart rate information inductively as one or more magnetic pulses per heart beat, for instance, to a wrist-worn receiver unit. On the basis of the received magnetic pulses, the receiver unit calculates the heart rate and, when needed, other heart rate variables, such as moving standard deviation of the heart rate. Often, the receiver unit, i.e. the wrist monitor, also comprises a display for showing the heart rate information to the exerciser and a user interface for the use of other facilities of the heart rate monitor. In the above-described situation, the heart rate monitor refers to the entity consisting of the electrode belt and the receiver unit. The heart rate monitor can also be a one-piece device in which the display means are located on the chest, and thus there is no need to transmit the information to a separate receiver unit. Further, the structure of the heart rate monitor can be such that it only comprises a wrist-worn monitor which operates without the electrode belt to be fitted around the chest, measuring the heart rate information from the vessel pressure. In the description of the invention, the heart rate measuring arrangement refers to the above-described heart rate monitor solutions. The heart rate measuring arrangement also comprises solutions in which heart rate information is transmitted to an external computer or to a data network, which has display means, such as a computer screen, for presenting the information measured or generated by the heart rate monitor.
In a preferred embodiment of the invention, the functions required by the method of the invention are performed in the receiving unit if the heart rate monitor consists of two pieces. One or more mathematical models of the invention and other functions required by the model are preferably implemented by software for a general-purpose processor. The models and functions can also be implemented as ASIC, with separate logic components or in a corresponding manner. In a preferred embodiment of the invention, the heart rate monitor comprises means for feeding user-specific physiological information, stress information and information on a fitness exercise. The feeding means can be, for instance, a keypad of the heart rate monitor, display equipment that supports control, a speech controller, a telecommunications port for external control or the like. The heart rate monitor also preferably comprises means for controlling the exerciser during a recovery exercise. The controlling means can be e.g. the display of a heart rate monitor, a speech controller, a telecommunications port for transmitting information to external means, such as a computer, or the like.
An advantage of the invention is that it provides more accurate controlling of recovery from a fitness exercise than the prior art methods.